1. Field of the Invention
This invention relates generally to electronic calculators, more particularly to a pocket electronic calculator having interchangeable components.
2. Prior Art
Present pocket calculators include, as a minimum, a keyboard, display, display driver electronics, processor or arithmetic electronics, batteries and case. With the exception of those calculators having programming electronics, the only major difference between one type of calculator and another type is that different arithmetic electronics are employed for each. That is, the same or similar type of keyboard, display, display drivers, batteries and case can be employed for all pocket calculators. However, the arithmetic unit of each different type of pocket calculator is different, since different functions are performed by each. Since a pocket calculator has a limited amount of space for keys, the number of functions which can be performed by that calculator are also limited. In order to overcome this problem, each key may be capable of performing more than one function if a shift or prefix key is provided to shift to a different level of arithmetic computation.
When a plurality of functions are assigned to each key of a calculator and shift or prefix keys are employed to change from one function to another function, the arithmetic unit (processing electronics) is relatively large. Any increase in the size of an arithmetic unit decreases the yield of that unit during its manufacture and increases its cost. Furthermore, the multiple functions performed by each key are confusing to a user. One pocket calculator which is presently on the market employs indicia on the top of each key, on the side of the keys, and adjacent each key on the case to indicate the three separate functions which can be performed by that particular key. It can be appreciated that a user may encounter some difficulty in being able to read the indicia associated with each key.
A pocket calculator having a plurality of levels, each corresponding to a different function of each key, may not be desirable for the user, since many of the available functions may not be applicable to his particular needs. However, in order to have some functions available which may be useful to a particular user, he is compelled to purchase a calculator containing other functions which are not applicable to his needs. Furthermore, the needs of a particular user may change from time to time, or additional functions which were previously unavailable may become available in the future in pocket calculators. The user, however, with present calculator configurations cannot avail himself of such additional functions, either as his needs change or as such functions become available, unless he purchases an entirely new and different calculator. That is, it is not now possible for a user to update his pocket calculator with additional functions.
Accordingly, it can be appreciated that a need exists for a pocket calculator which will provide only those functions which are desired by each particular user. A need also exists for a pocket calculator which can be updated with additional functions. Furthermore, a need exists for such a calculator which is relatively inexpensive and uncomplicated.